That was cool. I remember that science experiment in school. It is amazing how that stuff reacts with water. I am going to figure out the biproducts of the reaction for you to see how harmful it really was.

Alright got it. [Na(s) + H2O(l) --> NaOH(aq) + H2(g) + heat] So, in a nut shell, the pure sodium (solid) goes in the water and reacts to create sodium hydroxide (liquid) and hydrogen (gas) and heat. The flames you are seeing would be the heat igniting the biproduct hydrogen. It is amazing I still have my notes from HS chemistry.

quote from Wikipedia.

Sodium hydroxide (NaOH), also known as lye or caustic soda, is a caustic metallic base. Forming a strongly alkaline solution when dissolved in a solvent such as water, caustic soda is widely used in many industries, mostly as a strong chemical base in the manufacture of pulp and paper, textiles, drinking water, soaps and detergents. Worldwide production in 1998 was around 45 million tonnes. Sodium hydroxide is also the most common base used in chemical laboratories, and it also widely used as a drain cleaner.